1. Field of the Invention
The present invention relates to a rotation detecting device and a rotation detecting method for determining normal rotation/reverse rotation of a rotating shaft based on rotation signals different between normal rotation and reverse rotation of the rotating shaft.
2. Description of Related Art
In Japanese Laid-open (Kokai) Patent Application Publication No. 2009-002193, an engine control apparatus including a detector for outputting rotation signals in synchronization with rotation of a crankshaft of an engine, is disclosed. Here, the detector outputs the rotation signals of different pulse widths depending on whether the crankshaft is rotating normally or reversely. The control apparatus measures the pulse width of the rotation signal and determines the normal rotation/reverse rotation of the crankshaft based on whether or not the measured value of the pulse width is greater than a threshold value.
However, if the pulse width of the rotation signal varies due to variation between detectors or deterioration of the detector, it reduces accuracy of determination of the normal rotation/reverse rotation based on comparison between the measured value of the pulse width and the threshold value.